Resins



Aug. 21, 1945.

WITNESSES:

w. c. WELTMAN 2,383,430

RESINS Filed July l5, 1942 ,f-l/Pf/ux/'ny CO/zmf? 50! `Macau/7? "'50 50 Chem/fam? Ufa/ys?" Q if] Q v donde/7.50 7@ phenolic resins.

Patented Aug. 2l, 1945 UNITED STATES PATENT GFFIC RESINS William C. Weitman, Wilklnsburz, Pa., assigner to Westinghouse Electric Corporation, East Pittsburgh, Pa.. a corporation of Pennsylvania Application July 15, 1942, 'Serial No. 451,035

more parwidespread use in the arts and industries due to their low cost, ease of manufacture and superior mechanical and chemical characteristics. When combined with llers to produce laminated products, moldings embodying the phenol resins have exhibited characteristics which are superior on many counts to other synthetic resins. Accordingly, the production and use of phenol resins exceed that of practically all of the other synthetic resins combined.

The phenol synthetic resins are subject to certain drawbacks in applications for which they are otherwise admirably suited. A serious drawback is the fact that light colors and transparent sec tions are not easily obtainable in phenol resins. Ultra-violet light causes rapid deterioration in Several other resins have hetter abrasion resistance properties than is possessed by phenol resins. In addition, most phenolic resins as prepared heretofore have had a characteristic pungent odor. Therefore, it is desirable in some instances to combine a resin having superior appearance, odor and abrasion resisting characteristics as a surface layeron a body of e. phenolic resin which has lower cost and better strength characteristics.

'Up to the present time, the main factor which 1 hindered the application of surface layers of resins with certain. desirable properties upon a phenolic resin was the fact that the two resins would not bond satisfactorily. Some attempts have been made in the prior art to provide for combining two dissimilar synthetic resins of this Atype by mechanical expedientefor example, ap-

plying a layer of phenol resin to one side of a 'paper filler sheet and a surface layer of another resin on the other side of the same filler sheet. The mier sheet acts in this case as a combining or uniting medium` for the two resins. However, the two resins do not come in contact or bond with each other. Since the union between the 5 claims, (on. esc-sc) superior to those possessed by phenol resins of the prior art. In particular, the phenol resin may be polymerized at temperatures of 140 C. and lower to produce an inusible condensate which is relatively odorless and has good moisture resistance. e 4

Another highly desirable feature of the resin of this invention ls the property of withstanding a number of heat-treatments without being rendered infusible. Thus a solution of the resin y vmay be applied and heat treated to remove the solvent. Other resin solutions may be applied subsequently and each heat-treated without the phenolic resin becoming infusible or losing its moldability.

The object of this invention is to provide a phenolic resin which will thermoset or become L iniusible at a low temperature.

Another object of this invention is to provide for a phenol varnish material suitable for impregnating ller material and capable of being heat-treated several times without losing its moldability.

A further object of the invention is to provide for a phenol resin which will bond with other synthetic resins to form a strong union with the other synthetic resin. y

For a fuller understanding'A of the nature and objects of the invention, reference may be had to the following detailed description taken in conjunction with the accompanying drawing, in which the single gure of the drawing is a view partly in section through a reaction vessel.

In the present state of the synthetic resin art,

low cost lach some surface nish characteristics e e and are not available in a wide range of colors. The phenol resins are available mainly in dark if@ colors, and they do not exhibit the polish and eye appeal that is highly desirable in modern merchandise. Many available synthetic resins other than phenol resins exhibit superior abrasiomand lasting characteristics.

In particular, the urea resins'though more' costly than the phenolics, have advantages in point of color and surface finish. Pigmented urea-formaldehyde resins are available in all colors ranging from pure white to any desired hue in the spectrum'. Urea-.resins furthermore are highly resistant to abrasion, chemical reagents, moisture, ultra-violet light, and the effect oi various -gases present in .the atmosphere. They are substantially odorless as well.

In order to combine satisfactorily a phenolicresin with a surface layer of a resin, such, for

example, as the urea resin above-mentioned, it is the purpose oi the inventionvto produce a phenolic resin varnish whichl will. bond satisfactorily directly with the urea. resin. TheY requirements storage.-

of bonding with urea resin include the necessity for polymerization :of the phenol base varnish into theinfusible or C-stage *resinat temperatures of the order of 140 C. or lower, since above 140 C. the urea resins darken and decompose rapidly. The phenolic resin of the invention meets this requirement. The copending-patent application of H. C. Guhl, Serial No. 347,233, flied July 24, 1940, now Patent No. 2,292,118, discloses a product of-this type. f

In addition, the phenol base varnish which is produced by this invention is entirely stable in The varnish will not thicken to any appreciable extent at room temperature after being in storage for a time period of over one month. There is no appreciable chemical change in the varnish after being stored for a period of time of this length.

It has been found that when combined with nller material, such as cellulose paper or cloth, glass cloth and the like, the phenol base varnish producedby this invention has highly satisfactory greennesa conjoint property of moldability and exudation y which is determined for a sheet of ller material impregnated with a phenol .base varnish and dried; When two resin impregnated sheets cannot be molded into a unit, the resin is said to have lost its greennessf Under heat and pressure,-a certain amount of the varnish will exude in a fused stateout of the ller sheets while being molded. While ordinarily moldability and exudation are closely related, it has been discoveredA that for the phenol varnish of this invention, the exudation from a :dller having 50% to '70% by weight of resin under pressure of 1000 pounds per square inch at 150 C. may be as low as 1% while the varnish still retains a high degree ofv moldability. Greenness for the purpose of this invention may be defined as thevpercent of exudation of the resinous impregnant from a filler material, while the treated material is still moldable under a pressure of 1000 pounds per square inch ata temperature of 150 C. It has been found that the varnish produced by the process hereinafter described has a greenness of less than 1% to .5%. while retaining satisfactory molding properties. For ,certain purposes such low greenness is highly desirable since no striking through a surface layer of another resin on the same piece of ller occurs. In addition, wastage of resin minimized/ In 'the production of the type of phenol base' resin varnish'hereinbefore referred to, the base materials are phenols and formaldehyde, formaldehyde isomers and other aldehydes as well known to those skilled in the art. A particularly satisfactory phenol for this purpose is the ,mixture of cresols and xylenols, commercially known as cresylic acid. Ordinary phenol and meta-para cresol have been used with success. However, other phenols may be used for preparing this varnish. y

A 40% formaldehyde is employed for reaction with the cresylic acid, since it is a standard material available on the market. Formaldehyde base materiala'suchl as the various isomers of formaldehyde and related substances, may be substituted for the 40% formaldehyde solution 7 above indicated. The specific process hereinafter 'detailed will be described in reference to 40% formaldehyde solution, but substitution of these vlriousother formaldehyde base materials will be obvios to those skilled in the art.

This property of "greenness is av '30 centrifuge or other clarifying apparatus.

by'exudation from the ller is In preparing the resin, a closed reaction vessel Il, suchas disclosed by the single figure of the drawing, is ordinarily employed. The reaction vessel, vIII is composed of a main body I2 and a 5 cover I4 which may be hermetically attached to the body I2 by fastening means i6 and suitable gaskets. In order to promote a complete and thorough reaction, a stirring propeller Il is provided. Itis operated by shaft 20 passing through stuiiing box 22. A motor (not shown) drives shaft 20. Surrounding the body I2 of the reaction vessel is a steam jacket 24 supplied with steam by a line 26. Steam condensate is vented at 28.

The chemicals are introduced into the reaction vessel through a filling inlet 30. The cresylic acid and formaldehyde may be introduced by a pipe line 32 connected to suitable containers (not shown) from which weighed portions of reactants may be obtained. Valve 34 regulates entry of the reactants.

A second line 36 is connected to the inlet 30 in order to provide for the introduction of polymerizing catalysts. Valve 38 controls the catalyst line 36. In addition, a. vacuum line 40 con.

trolled by valve 42 is connected to inlet 30. After the reaction has progressed to the desired point, the contents of the closed reaction vessel may be dumped through the outlet 44 which leads to a A control valve 46 is placed in outlet line 44.

In case refiuxirg is desired, the reiluxing column 50 is attached to the cover I4. Valve 48 con- 3'5 trois the passage of gaseous constituents tothe column 50. Pipes 52 and 54 are the inlet and outlet, respectively, of cooling water to the reflux column 50 to cause condensation of vapors.

In producing phenolic resin of this invention having the particularly desirable properties set forth herein, one mol of phenol is combined with from 0.8`to 1.2 mols of aldehyde, such as formaldehyde. Any greater excess of formaldehyde is not only unnecessary but leads to several undesirable results. Whenv 1.5 mols ofr formaldehyde per mol of phenol are employed in the reaction the resulting resin gives ofla strong odor, particularly when wet 0r when moisture is present. The excessive amount of formaldehyde also renders the resin much more reactive and more responsiveto heat-treatment to reach aninfusible Parts 1. Cresylic unid 1250 40% formaldehyde 840 2. Meta-para cres'ol 1200 40% formaldehyde 150 o) 40% formaldehyde 600 weighed quantities 'of the'phenol and amehyde are introduced into the reaction vessel I0 throuhy line 32-3., valve 34 being closed after the ingredients have been introduced into the vessel.

in motion and steam is admitted to jacket 24 group are potassiumv hydroxide, sodium hydrox@A ide, calcium hydroxide and barium hydroxide.

In some instances it has been found satisfacvtory to vary the amount of the catalyst from Ve to l part for 100 parts of the phenol, the time of reuxing and stirring of the catalysts with the reactants 'inversely corresponding to one-half hour for one-third of 1% of catalyst. Thus one hour of refluxing is'required for 1/6 part of catalyst per 100 parts of the phenol, as cresylic acid.

At the end of this time period a certain amount and type of resinication between the cresylic acid and formaldehyde has occurred. The resin at this stage is satisfactory for some uses. It has heen found, however, that better ageing and thickening characteristics during storage are achieved by 'removing the metallic hydroxide vcatalyst and substituting a secondary catalyst and further continuing the reaction which promotes a dierent type of reaction and advances the degree oi resiniiication after this initial stage.

At the end of the time period corresponding to one-haii hour for 1/3 part of metallic hydroxide catalyst perl6@ parts of phenol, the vacuum line valve it is opened and vacuum applied to the contents of the reaction vessel. Both. moisture and excess formaldehyde are withdrawn by the evacuation treatment. Within a short time after the evacuation has heen-started, the secondary catalyst may he iritroducedthroug'h line llt ley opening valve t@ while closing valve it tempo rarily.

The secondary catalyst which it is preferred tc use in this application consists in part oi an ammonium salt, which, when introduced into the initial reaction mixture, will form a metallic salt precipitate with the alkali or alkaline earth metal and ammonium hydroxide from the hydroxide radical or the catalyst present. Ammonium sultate has been particularly successful in achieving this chemical reaction. Ammoniumgi sulfate in quantities suilicient to react with substantially all the sodium hydroxide, for example, to form sotemperature of the reaction mixture so that overheating does not readily occur.

The second stage of polymerization is allowed to proceed for a time period of from one and one-half to two' and one-half hours, at the end f of which. period the material within the reaction vessel is, a^^tliickvisccus resin and substantially all of the moisture has been removed. It is believed that any unreacted excess of formaldehyde has either been removed or is combined with the ammonia to form hexamethylenetetramine. Dispersed within this rinous mass is a small amount of sodium sulfate precipitate. The product is substantiallyan A-stage phenol formaldehyde resin.

In order to provide for applying the resin to fabrics or paper illm, 70 to 100 parts of a solvent consisting of from .to 100 parts of ethyl alcohol and up to parts of benzene solvents, such as benzol, toluene, xylene andother phenol-formaldehyde solvents or other suitable solvents are added to the resin. A satisfactory mixture consists of 50% ethyl alcohol and 50% benzol. Ethyl alcohol alone is also a satisfactory solvent. This solvent may be introduced through the chemical pipe line 32 and valve 34. stirring the solvent into the resin win-kin ehevreacuon. The viscous dium sulfate and ammonium hydroxide, is introduced as a water solution. The sodium sulfate precipitates in the phenol formaldehyde'resinous product when the water has been removedAl by evacuation. l

Additional, ammonium hydroxide is also added in order to cause the second stage of resiniilcation to proceedy usually from 2 to 4 parts of 30% aqua ammonia solution is added and the contente .l stirred for a short time.

Thereafter the vacuum line valve 62- is opened resinous product will be thinned out suiiiciently by the addition of the solvent for easier storage and later application.

The valve 40 is now opened and the contents of the reaction vessel are put through a centrifuge or other clarifying apparatus (not shown) in order to remove the sodium sulfate or other precipitate and to clarify the resinous solution ci deleterious substances. The clarified product constitutes a phenolic varnish which is suitahle icr impregnation oi? fabric, paper or other hller r is removed by scraping, and thereafter a coating ot urea formaldehyde or melamine resin is applied to the scraped side of the impregnated and dried sheet. This sheet is particularly useful as a decorative top or surface sheet to be bonded to a lease ci regular phenol formaldehyde material. The aforementioned copending Patent 2,292,lld discloses such a material in detail.

Good houding of the urea resin surface layer to the phenolic base is necessary in order to prevent moisture penetrating and causing the de lation of the urea resin surface from the phenolic resin body. When in use, decorative panels ci this type oi material may be subjected to conditions of high humidity, or even repeatedly wetted,l asv during cleaning thereof. Moisture resistance is a critical characteristic or the bond.

)In preparing decorative surface sheets by applying urea-formaldehyde or a mele aidehyde resin to a sheet impregnated with the phenolic resin, it is necessary .to heat treat the phenolic resin twice. Initially the phenolic resin solvent and to convert .the resin to the B-staae.l

The urea-formaldehyde resin is then applied as apaint or Varnish to the scraped surfacerand a second heat-treatment at temperatures of from to 125"A C. is employed to remove the solvent.

In both cases .the temperatures are high enough to carry the degree of polymerization forward and ordinary phenolic resins would become completely infusible after the second heat treatment. Reaching an infusible state at this point would defeat the purpose for .which the top sheets were prepared-namely, molding with an all phenolic base panel. The phenolic resin produced by this factorily with minute flow out of the filler. This -extremely low exudation is a considerable advance over the customary prior art resins where exudation of the order of for corresponding I amounts of resin is regarded as necessary to i secure good molding and bonding between laminations.

Experimental tests of laminated articles embodying a decorative surface consisting of urea resin bonded with the phenolic resin producedl by this invention confirm the exceptional characteristics of the bond. The low greenness, less than 1%, ofthe phenolic resin has reduced any striking of the resin through the urea resin surface layer to 'a negligible amount. The moldability and bonding, however.' have been as` good as or even exceeded those exhibited by any prior art phenolic resin. Panels of this kind have been subjected to boiling water. for periods of over two hours without any sign of delamination of the urea resin from the present phenolic resin. On the other hand, laminated panels conforming to the best practice of the prior art, when subjected to boiling water delaminated in a few minutes and the urea layer lifted oil.

As hereinbefore. mentioned, thephenol resin produced by the above process is extremely stable in storage in that it does not thicken or deteriorate chemically. Even after months, its greenness or flow under selected standard conditions is low, while adequate moldability is retained.

The resin actually bonds with urea to form a firm and stable composite article. Ihe phenol resin will polymerize to the lnfusible or C-'stage at temperatures of 140 Cfor lower with a satis factory molding cycle. 'l'his relatively low temperature is particularly important in treating urea-aldehyde resins, since the'urea resins, will decompose rapidly at higher temperatures.

The phenolic varnish produced by the above Since certain obvious changes may be made in the above procedure and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting Sense.

capable of bonding to urea resins and polymeriz- -ing at temperatures of about 140 C. and lower into an odorless and infusible condensate, compris-ing the reaction product of l'mol of a phenol and from 0.8 to 1.2 emols of 40% formaldehyde monium hydroxide catalyst, and a solvent for the resin, the resin and solvent combined to produce Va liquid varnish.

2. The method of preparing a phenolic base Aimpregnating varnish having good lo'w greenness when combined with a ller, capable of polymerizing at temperatures of about 140 C. or below into an infusible body, which comprises reacting at about the boiling point of the mixture 1.0 mol of a phenol and from 0.8 to 1.2 mols of formaldehyde with from about 1/e% to 1% of the weight of the phenol of an alkali hydroxide catalyst to effect an initial reaction, evacuating to remove unreacted formaldehyde and water, the initial reaction being conducted for a period of time inversely proportional to the amount of catalyst and corresponding to about one-half hour for 1/;%, introducing an ammonium salt and ammonium hydroxide into the partially reacted mixture, the ammonium salt chemically reacting with the alkali hydroxide to produce an alkali salt, which will precipitate, and ammonium hydroxide, the total ammonium hydroxide effecting .a secondary catalytic reaction to produce a resinied material, dissolvingv the resiniiied material in a solvent and centrifuging the resin solution to remove the alkali salt precipitate and to effect clarication.

3. The method of producing a phenolic base resin varnish capable of polymerizing at temperatures of about 140 C. or below into an infusible condensate, which comprises reacting at about the boiling point of the mixture 1.0 mol of a phenol and from about 0.8 to 1.2 mols of formaldehyde, in the presence' of an initial catalyst selected from the hydroxides of the group consisting of alkali metals and alkaliine earth metals to produce a partial reaction of the bases, and after a period of time corresponding to about one-half hour for V;% of catalyst based on the weight of the phenol evacuating to remove unreacted formaldehyde and water, thereafter introducing ammonium sulfate into the initial reaction product in suilicient amount to provide for a substantially complete precipitate of the sulfate of the metal present as the hydroxide and to produce ammonium the centrifuged solution being a stable, substantially non-ageing resin varnish, which when ap'- plied to ller material and molded has high viscosity.' good low greenness, is capable of bonding with urea resins and produces an odorless, molsture-resisting solid. y

4. 'Ihe method of producing a phenolic base resin varnish capable of polymerizing at temperatures below 140 C. into an odorless and moisture-resisting infusible condensate, which comprises reacting in a closed reaction vessel 1 mol ofl a phenol and from about 0.8 to 1.2 mols of 40% and Vs to Ipartofacata-` formaldehyde solution lyst per 100 parts of phenol selected from the i hydroxides of the group consisting of alkali nietals and alkaline earth metals, thewhole being reiiuxed for a time period corresponding to about one-half hour for V3 part of catalyst'to eiect an initial reaction, the time of reiluxing being inversely proportional to the amount of catalyst present, yevacuating the reaction vessel at the termination of the time period to remove 'water and unreacted formaldehyde, adding sufficient ammonium sulfate to chemically react with substantially all of thel metal hydroxide to provide for a precipitate of metal sulfate-and to produce ammonium hydroxide, and further adding 2 to 4 parts of 30% aqueous ammonium hydroxide solution per 100 parts of phenol, the total ammonium hydroxide causing a secondary reaction between the phenol and formaldehyde to produce a resinous substance, the temperature in the reacting mixture beingmaintained at about'50 to 70 C. while moisture is being evacuated and reaching a `final temperature of 85 C. to 110 C., introducing a solvent into the reaction vessel after the secfondary reaction has proceeded one and one-half to two and one-half hours to produce a resinous varnish solution and removing the precipitated metal sulfate from the varnish solution.

5. 'I'he method of producing a phenolic base resin varnish capable of polymerizing at temperatures below 140 C. into an odorless and moisture-resisting infusible condensate', which com- Prisesl in a closed reaction vessel 1.0 mols of cresylic acid and from about 0.8 to 1.2 mols of 40% formaldehyde solution and Ve to lfpart of a catalyst per 100 parts of thecresylic acid selected from the hydroxides yof the group consisting of the alkali metals and alkaline earth metals, the whole being reiluxed for a time period corresponding to about one-half hour for le part of catalyst to eiect an initial reaction, the time of reiluxing being inversely proportional to the amount of catalyst present, evacuating the reaction vessel at the termination of the time period to remove water and unreacted formaldehyde, adding sufcient ammonium sulfate to chemically react with substantially all of the metal hydroxide to providefor a precipitate of metal sulfate and to produce' ammoniumy hydroxide, and further adding 2 to 4 parts of 30% aqueous ammonium hydroxide solution per 100 parts of cresylic acid, the total ammonium hydroxide causing a secondary reaction between the cresylic acid and formaldehyde to produce a resinous substance, the temperature inthe reacting mixture being maintained by heating to about to 70C. during i moisture removal by evacuationand reachingfa y final temperature of C.l to 110, C.',.lntroduc and 0 to 50 parts oi' benzene Solvent.

a solvent intcthereaction vessel after the WILLIAM C. WELTNIAN. 

